subtilis. This result may be explained, taking into account the fact that many interactions relating to every gene in the network have still not been discovered and it is also RGFP966 probable that

the degree of sensitivity in the microarray analysis was not sufficient to detect every significant signal. Our analysis revealed other expressed genes regulated by non-orthologous TFs that manifest similar functions. These consist of the cases of FruR (E. coli) and CcgR (B. subtilis), controlling the central intermediary metabolism, as well as RbsR (E. coli) and AbrB (B. subtilis), repressing genes in the presence of ribose. For instance, the AbrB, evolved to respond to additional stimulus, extending the number of elements of the regulon to sporulating functions. Finally, our results indicated that the SOS regulon control on the part of the orthologous TF LexA was not conserved [26]. The examples described previously are consistent with other findings indicating that the conservation between regulatory networks of distant organisms is in fact limited., Arguments treating this subject are directed towards the possibility mTOR inhibitor of genetic duplication [40] and the adaptation

of each organism to particular media [27, 28], also promoting the concept that proteins evolved and took on new functions. Comparison of topological units of the sub-networks between E. coli and B. subtilis There is convincing evidence to suggest that gene duplication is a major force explaining the growth of TRNs [27, 28, 40]. It is possible that this modifying process affects the connectivity distribution of these networks, as has been observed in other biological networks [27]. In view of these findings, we compared the modular structures found in E. coli and B. subtilis, in order to evaluate

the conservation of topological structures. A comparison was carried out, considering the modular structure of the sub-network of E. coli in the presence of glucose [13] and the modular structure for B. subtilis, generated during this study. Figure 4 presents orthologous genes that were organized into modular structures. At this level, we could see that most of the genes clustering in modules in both sub-networks, related to carbon metabolism. Those genes encoding for proteins of the PTS system were outstanding (levDE, ptsG), the degradative next enzyme galK and the gene rbsB encoding as a transporter. All of the genes previously described except ptsG belong to the modules classified as Carbon Modules in both sub-networks. In the case of E. coli, genes in this module were clustered because they were regulated by CRP and in the case of B. subtilis by the relationship of the genes to the regulatory protein CcpA. The disconnection of ptsG from the carbon module in B. subtilis can be explained by the absence of regulation by CcpA (Figure 4, Table 1). Figure 4 Conserved glucose responding modules between B. subtilis and E. coli.